Suppose you were planning to retire in 2018, and you sold in 2008 or 2009 after the economy crashed. Bad things would happen. No one knew if or how fast the stock market would come back. Better to sell a little bit over time and move to safer investments. But there are many studies showing no one can time the market.
Agreed - perhaps I phrased it incorrectly, but I meant to say the you start moving investments out of the market 10 years prior to your retirement date, not that you sell everything in one huge move at the 10 year mark.
